1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor substrate provided with a through hole electrode.
2. Description of the Related Art
Semiconductor substrates provided with a through hole electrode have been used for electrical connections of various types of electronic devices, optical devices and the like, or as an interposer for three-dimensional (3D) stacked devices.
FIG. 1 is a schematic cross section view showing an example of a semiconductor substrate provided with a through hole electrode.
This semiconductor substrate provided with a through hole electrode is composed of a semiconductor substrate 1 made of a silicon substrate and the like, a small hole 4 formed through the semiconductor substrate 1, an insulating layer 2 formed on the opposites surfaces of the semiconductor substrate 1 and also on the inside surface or side wall of the small hole 4, and a through hole electrode 3 made of a conductive material such as a metal with which the small hole 4 is filled.
With reference to FIG. 2A to FIG. 2C, the manufacturing method of such a semiconductor substrate will be explained as an example of a conventional technique.
First of all, as illustrated in FIG. 2A, the small hole 4 is formed through the semiconductor substrate 1 (a small hole formation step). The small hole 4 can be formed by DRIE (Deep-Reactive Ion Etching) as typified by ICP-RIE (Inductively Coupled Plasma-Reactive Ion Etching), anisotropic etching making use of a potassium hydroxide solution and the like, microscopic machining with a microdrill, Photo Assisted Electro-Chemical Etching, and so forth.
Then, as illustrated in FIG. 2B, the insulating layer 2 is formed on the opposites surfaces of the semiconductor substrate 1 and on the inside surfaces of the small hole 4 (an insulating layer formation step).
Next, as illustrated in FIG. 2C, the small hole 4 is filled with a conductive material such as a metal by a Molten Metal Suction Method, a sputtering method, a plating method, a screen printing method and the like to form a through hole electrode 3.
The semiconductor substrate provided with a through hole electrode manufactured in this manner can be used as an interposer which can be used in 3D stacking as shown in FIG. 3.
As described above, in accordance with the conventional manufacturing method of a semiconductor substrate provided with a through hole electrode, various types of electronic devices and electrical wiring patterns as required are fabricated after forming a through hole electrode in a semiconductor substrate. Because of this, there is restriction in process temperatures as available, when thermal treatments are performed after forming a through hole electrode in a semiconductor substrate, depending upon the properties of the conductive material of the through hole electrode, and therefore the selection of devices and wiring patterns which can be formed thereon is limited.
For example, while sintering is performed at about 400° C. to form the wiring pattern made of aluminum, the through hole electrode may become molten or the properties thereof may be altered by the thermal treatment in the case where the through hole electrode is made of a conductive paste or a eutectic metal such as gold and tin (Au—Sn).
Also, in the case where electric devices are fabricated on the semiconductor substrate provided with a through hole electrode, there are following problems relating to the fabrication process thereof.
In usual cases, from the viewpoint of heavy metal contamination, it is preferable, when possible, not to bring a metal other than a conventional wiring metal such as aluminum in a clean room where electric devices are fabricated. The fabrication process for fabricating electronic devices and electrical wiring patterns in a semiconductor substrate provided with a through hole electrode is not preferred from the viewpoint of controlling contamination because the process are carried out using a plurality of equipments such as a deposition system, a pattern aligner and so forth. If a semiconductor substrate provided with a through hole electrode or a device fabricated thereon is contaminated, the characteristics of not only the semiconductor substrate itself but also of other electric devices having no through hole electrode is deteriorated due to the cross contamination via these equipments. Accordingly, when a through hole electrode is used in an electric device, it is desirable to move the step of forming the through hole electrode to the final stage of the manufacturing method as much as possible.
Moreover, since there are usually formed irregularities of the order of several micrometers on the surface of a through hole electrode, the fabrication process is hampered by the irregularities, depending upon the device to be fabricated. For example, when a resist is coated on a semiconductor substrate provided with a through hole electrode by means of a spin coater, it becomes difficult to form a resist film in a uniform manner in the vicinity of the irregularities on the surface of the through hole electrode.
The present invention has been made in order to solve the shortcomings as described above. It is an object of the present invention therefore to provide a manufacturing method of a semiconductor substrate provided with a through hole electrode wherein it is possible to effectively form a through hole electrode in a semiconductor substrate provided with a device and a wiring pattern.